• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.61-68
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• 2017

Electrochemical conversion of $CO_2$ and production of $H_2$ were attempted on a three-dimensionally ordered, porous metal organic framework (MOF-74) in which transition metals (Co, Ni, and Zn) were impregnated. A lab-scale proton exchange membrane-based electrolyzer was fabricated and used for the reduction of $CO_2$. Real-time gas chromatography enabled the instantaneous measurement of the amount of carbon monoxide and hydrogen produced. Comprehensive calculations, based on electrochemical measurements and gaseous product analysis, presented a time-dependent selectivity of the produced gases. M-MOF-74 samples with different central metals were successfully obtained because of the simple synthetic process. It was revealed that Co- and Ni-MOF-74 selectively produce hydrogen gas, while Zn-MOF-74 successfully generates a mixture of carbon monoxide and hydrogen. The results indicated that M-MOF-74 can be used as an electrocatalyst to selectively convert $CO_2$ into useful chemicals.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1150-1154
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• 2001

Silicon oxynitride (SiON) thick films using the core layer of silica optical waveguide have been deposited on Si wafer by PECVD at low temperature (32$0^{\circ}C$) were obtained by decomposition of appropriate mixture of (SiH$_4$+$N_2$O+$N_2$) gaseous mixtures under RF power and SiH$_4$/($N_2$O+$N_2$) ratio deposition condition. Prism coupler measurements show that the refractive indices of SiON layers range from 1.4663 to 1.5496. A high SiH$_4$/($N_2$O+$N_2$) of 0.33 and deposition power of 150 W leads to deposition rates of up to 8.67 ${\mu}{\textrm}{m}$/h. With decreasing SiH$_4$/($N_2$O+$N_2$) ratio, the SiON layer become smooth from 41$\AA$ to 6$\AA$.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.616-624
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• 2011

Hydrogen storage and release of Fe/Zr/Mo mixed oxide mediums were investigated by hydrogen reduction and water splitting oxidation($Fe_3O_4+4H_2{\rightleftharpoons}3Fe+4H_2O$). As the results of TPR/O, Mo was an additive to enhance the reactivity of water splitting oxidation as well as the stability of the medium. On the other hand, it seemed that $ZrO_2$ additive provided the passway for the diffusion of gaseous chemicals on the medium in repeated redox cycles. Among the Fe/Zr/Mo mediums, a FeZrMo-7 medium (Fe/Zr/Mo=80/13/7mol%) exhibited the best performance with good durability during five repeated redox cycles. The amount of hydrogen evolved on the medium was maintained at ca. 10.7mmol-$H_2$/g-medium corresponding to the hydrogen storage amount of ca. 2.2wt%.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.3
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• pp.227-240
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• 2010

Coal gasification is heading for a great future as one of the cleanest energy sources, which can produce not only electricity and heat, but also gaseous and liquid fuels from the synthesis. The work focuses on 300MW shell type one-stage entrained flow coal gasifier which is used in the Integrated coal Gasification Combined Cycle(IGCC) plant as a reactor. As constructing an IGCC plant is considerably complicated and expensive compared with a pulverized-coal power plant, it is important to determine optimum design factors and operating conditions using a computational fluid dynamics (CFD) model. In this study, the results of numerical calculations show that $O_2$/Coal ratio, 0.83, Steam/Coal ratio, 0.05, coal particle diameter, $100{\mu}m$, injection angle, $4^{\circ}$ (clockwise) are the most optimum in this research.

• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.15-20
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• 2011

Although CNG is able to meet the current emission standards, it is expected to be impossible to satisfy the requirements of the next EURO-6 emission regulation without an additional after-treatment device. Hydrogen is known to be a gaseous fuel which features the wide flammability limit and the fast reactivity. A certain amount of hydrogen addition to CNG is able to extend the lean combustion range and produce lesser amounts of harmful emissions. In this research, the combustion and emission characteristics of HCNG(mixture of Hydrogen and CNG) fuel were experimented in an 11-liter heavy duty lean burn engine varying hydrogen contents, air-to-fuel ratio and spark timing. The optimization of this HCNG engine for a city bus was performed through the evaluations of oxidation catalyst characteristics.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.12
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• pp.2199-2201
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• 2008

Sulfur hexafluoride($SF_6$) is a gaseous dielectric used in high voltage electrical equipment such as an insultor or arc quenching medium in the transmission and distribution of electricity. however, $SF_6$ is one of the greenhouse gases(GHG) with a global warming potential that is 23,900 times greater than that of carbon dioxide($CO_2$). for this reason, $SF_6$ emissions in electric equipment shall be controlled to reduce GHG and improve cost-effective use of $SF_6$ for economical benefits. Until recently there has not been any investigation on $SF_6$ emission characteristics and inventory in Korea. To understand emission characteristics during the use-phase, the scope of this study was limited to the following closed pressure system equipment from 10 substations in Korea. This study highlights (1) the investigation of sampling/analysis methodology for $SF_6$ emissions in high voltage equipment, (2) the estimation of $SF_6$ emissions in the use-phase, and (3) the comparison between the emission ratio and the mass-balance applied to inventory study. According to this study, the majority of emissions were related to electric equipment nameplates and the rest of the emissions were related to the handling of $SF_6$ during operations. from this result, emission ratios estimated from this study were similar; GIS was 14% and GCB was 13%, as maintenance process conditions were the same as manual process conditions for both equipment.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.356-360
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• 2014

The environmental pollution caused by green-house gases such as $SF_2$ has been becoming the main issue of industrial society. As a part of these efforts, 180 countries signed the Kyoto Protocol in 1997 to cut back on their green-house gas emissions [1]. Therefore, a study on the dielectric characteristics of the $GN_2$ is important for designing a eco-friendly high voltage apparatuses. In this paper, to develop an electrically reliable, stable, and eco-friendly high voltage apparatus, the breakdown voltage and partial discharge inception voltage characteristics in $GN_2$ considering utilization factors are studied for the establishment of insulation design criteria of an high voltage apparatus. Dielectric experiments are performed by using several kinds of sphere-plane electrode systems made of stainless steel. Also, the dielectric characteristics of the $GN_2$ are analyzed by using a Finite Elements Method (FEM) according to various field utilization factors. The results are expected to be applicable to designing the high voltage apparatuses using $GN_2$ as an insulation gas.

• Resources Recycling
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• v.16 no.6
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• pp.28-33
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• 2007

Coal is the most abundant energy source and deposited in every area of world. Combustion process with lower efficiency has been mainly used. Therefore, implementation of more efficient technologies, involving gasification, combined cycles and fuel cells, would be a key issue in the plans for more efficient power generation. In these technologies, gasification has been studied for decades. However, coal gasification to high value combustible gas such as hydrogen and carbon monoxide is focused again due to high oil price. The gaseous product, called syngas, can be effectively utilized in a variety of ways ranging from electricity production to chemical industry (as feedstock). In this study, coal gasification with ultra high temperature steam has been performed. The effect of steam/carbon ratio on the produced gas concentrations, gasification rate and additional products like tar, ammonia and cyan compounds has been determined.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1699-1701
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• 2000

The dynamic behavior of fatty acid monolayers at the air-water interface was investigated using a displacement current-measuring technique coupled with the so-called Langmuir film technique and also the dipole moment of the acids was determined. The displacement current flowing though a short circuit wan generated only when induced charges on an electrode flowing though suspended in air was changed by monolayer compression. The displacement current measurement was found to be a very sensitive method used for a better understanding of the relationship between the structure and function of the monolayers placed on the water surface and it was also found to be a very useful method for detecting the dynamic motion of molecules in the entire range from the so-called gaseous state to solid state at the same time. In the paper investigate fatty monolayer dynamic state and electric property character. As result. Displacement current generate higher nearly distance electrodel and water surface. Also, Molecule behavior was found pocess active higher thermal.

• Progress in Superconductivity and Cryogenics
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• v.13 no.4
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• pp.30-35
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• 2011

This paper describes experimental study and performance improvement of 2 stage Gifford-McMahon (G-M) type pulse tube cryocooler for cryopump. The objective of this study is to improve the efficiency of 2 stage pulse tube cryocooler for substituting 2 stage G-M cryocooler used in cryopump. The target cooling capacities are 5 W at 20 K and 35 W at 80 K for the $1^{st}$ and the $2^{nd}$ stage, respectively. These values are good cooling capacities for vacuum level in medium size ICP 200 cryopump. Design of the 2 stage pulse tube cryocooler is conducted by FZKPTR(Forschungs Zentrum Karlsruhe Pulse Tube Refrigerator) program. In order to improve the performance of 2 stage pulse tube cryocooler, U-type pulse tube cryocooler is fabricated and connecting tubes are minimized for reducing dead volumes and pressure losses. Also, to get larger capacities, orifice valves and double inlet valves are optimized and the compressor of 6 kW is used. On the latest unit, the lowest temperatures of 2 stage pulse tube cryocooler are 42 K ($1^{st}$ stage) and 8.3 K ($2^{nd}$ stage) and the cooling capacities are 40 W at 82.9 K ($1^{st}$ stage) and 10 W at 20.5 K ($2^{nd}$ stage) with 6.0 kW of compressor input power. This pulse tube cryocooler is suited for commercial medium size cryopump. In performance test of cryopump with 2 stage pulse tube cryocooler, pumping speed for gaseous nitrogen is 4,300 L/s and the ultimate vacuum pressure is $7.5{\times}10^{-10}$ mbar.